Ceramic article and method of making the same



June 19, 1923. 1,459,357

M. c. BOOZE CERAMIC ARTICLE AND METHOD OF MAKING THE SAME Original Filed Feb, 17. 1921 Iii/messes llII/dlI/0l' fiaadonald 6! 80020.

4y liar/u Patented June 19, 1923.

UNITED STATES PATENT OFFICE.

IACDONALD C. BOOZE, OF WORCESTER, MASSACHUSETTS,

a'ssrcnoa r0 noz'rox COI- CERAMIC ARTICLE AND METHOD 0! MAKING THE SAME.

Application filed February 17, 1921, Serial No. 445,888. Renewed December 8,

To all whom it may concern:

Be it known that I, MACDONALD C. Booze, a citizen of the United States of America, residing at Worcester, in the county of Worcester and State of Massachusetts, have invented certain new and useful Improvements in Ceramic Articles and Methods of Making the Same, of which the following is a full, clear, and exact specification.

My invention relates to a laminated article comprising ceramic bonded granular material and to a rocess of makin the same, and more particularly to a multilayer article which has an exposed or working face portion of a special composition and character to meet specific chemical, refractor or abrasive requirements, while the bac ing and bulk of the article is made of a cheaper and more easily fabricated mateial.

Certain uses of refractories, abrasive stones or non-slip tiles make it desirable or necessary that the face ortion only of the article contain super-re ractor or abrasive material. For example, a bric intended to be exposed to the destructive action of chemical gases, slag or molten baths, may have one face consisting mainly of crystalline alumina and the other face substantially the same as a fire brick. It also is not economically expedient to provide such an article with the expensive super-refractory or abrasive material throughout the entire structure where it is necessary that the surface portion only be of this protective or abrasive nature.

It has been proposed to make a refractory article of several layers containing silicon carbide in such decreasing amounts from the Facing towards the rear as will give a graduated and increasing coefficient of expansion. It is found, however, that such procedure results in a warped article if it is fired at such a high temperature as to cause material shrinkage of the clay backing, it

being evident that the silicon carbide facing will not shrink to the same extent as does the cla It is accordingly an object of my invention to overcome the o jectionable features found in prior articles of this type and to roduce a multilayer article which has a re ractory 1881. lerlal Io. 590,881.

or abrasive surface portion integrally united with a backing of a less refracto or abrasive mixture which may be fired at high temperatures without detrimental warpage and will be more economical than and as serviceable as an article which has a uniform structure throughout.

A further object of my invention is to rovide a feasible and economical metho of forming a ceramic article of the class described by substantiall equalizing the drying and burnin shrin ages in the different portions of sue]? a multilayer body whereby a facing containing a hi h content of preshrunk grains may remain integrally united with a backing of a different composition and the latter will not crack away or shrink to such an extent as to render the article defective. Other objects will be apparent in the following disclosure.

In accordance with my invention, I propose to make articles of this class by employing such compositions and methods of operation as will increase the dryin and burning shrinkage of a ceramic bo y containing su er-refractory material of low shrinkage va ue and to provide a multiple layer article by supplementing such rocedure with that involved in decreasing t e shrinkage of the portion which would normally shrink too much for use in an article of this t pe, or I may employ only the latter met 0d of equalizing shrinkage. I furthermore referably employ one or more interm iate layers of suitable compositions to avoid abrupt shrinkage differentials during drying and firing. The shrinkage of the facing is increased by employing a lar amount of water with the bond, while the backing may be maintained in a comparatively dry state so that elimination of moisture will not materiall affect the size of this portion of the artic e.

The most efficient preshrunk super-refractory materials adapted for refractory or abrasive purposes comprise such substances as silicon carbide, crystalline alumina, etc., and this invention is broadly applicable to all super-refractory and abrasive materials which may be bonded b ceramic bonds of the class herein described although my method is described herein with particular reference to but one of them. Crystalline alumina, which occurs in nature as corundum or in the various emerys and may be made artificially by fusing and crystallizing such substances as bauxite, containing various types and degrees of impurities adapted to modify the temper, the physical characteristics and the chemical composition of the crystallized grains, does not shrink materially when fired in the ordinary ceramic kiln, whereas the various clay materials used as bonds for the refractory grains and employed by themselves to form fire bricks have a large shrinkage during drying and burning. Hence, if one wishes to provide a fire brick or abrasive block with a facing of crystalline alumina, it is necessary to compensate for the difference of shrmkages during the manufacturing operations.

As one method of increasing the shrinkage of the facing of the article, which consists essentiall of super-refractory grains such as crystal ine alumina, I propose to utilize a ceramic bond therefor which contains an ingredient capable of providing a large degree of shrinkage during drying and preferably during both the drying and the burning operations. A substan'ce admirabl adapted for my purposes is bentonite, whic is a peculiar variety of clay found in the State of Wyoming, and is characterized mainly by the property of absorbing about three times its weight of water and swelling to a marked extent. \Vhile this clay varies considerably in composition, it ordinarily is ofa yellowish green color when fresh and assumes a light green to white color on exposure to the atmosphere. The clay, which has a specific gravity of about 2.18, is exceedingly fine grained and soft and is thought by some to be in a colloidal condition. A typical analysis of one of these clays is as follows:

A120, 18.97% FeQ, 1.85 did 33 p oiIIIIIIIIIIIIII 0:63 2.03 s3 0.69 6 8.08

By incorporating bentonite in the plastic clay material with which the alumina grains are bonded, I insure that upon mixing with water the alumina grains will be separated by the swelling of the bond, so that upon drying and burning, the mass will shrink more than if bentonite were not present. The rear portion of the article not containing this bentonite will shrink the normal amount, according to its composition.

Hence, by a proper ad'ustment of the amounts of bentomte use and the water contents of the different layers, I ma so adjust the shrinkage values of the ifierent portions that they will be substantially equalized.

I furthermore compensate for this shrinkage differential by incorporating in the backing a preshrunk refractory material in such proportions as to reduce the shrinkage of this ayer to the desired extent. An inexpensive material suitable for my purpose is fire clay grog, obtained by breaking up old saggers and baits which have reviouslv been fired at a temperature as high as that to which the new article will be heated, whereby the grog has been shrunk substantiall to its maximum extent, before use in the new article. The proportions of the refracto grog are determined by various factors, su h as t e nature of the clay materials employed and the amount of shrinkage compensation desired. 1, however, find that for this type of refractory I ordinarily utilize an amount of granulated grog far in excess of that heretofore specified and deemed the maximum for firebrick compositions. This is made ossi-ble by the use of a ball clay considera ly more plastic than the clays commonly employed in making fire bricks. It will be evident that if intermediate layers are employed, these will be made up of mixtures of the ingredients of the surface layers, with the essential materials, affecting the shrinkage decreasing in amount from one face toward the other, so that all the layers will shrink to substantially the same extent.

As a specific embodiment of my invention, reference is to be had to the accompanyin drawing which shows in a cross sectiona view a refractory brick made up of three layers, a front facing 1 consisting essentially of crystalline alumina bonded by a vitreous ceramic material, a refractory clay backing 2 such as burned fire clay and grog and an intermediate layer 3 of a mixture of the ingredients of the two outer portions. As a specific example of a composition which will be suitable for a fire brick capable of 1 withstanding heat treatment at Se 1' cone 15, as determined largely by the re ractoriness of the backing, the following table of ingredients and proportions is to be noted:

Ball clay 20% by weight.

Backing.

Fire cla 10 mesh and finer 75% by weight. Ball clay 25% by weight.

Water for each batch to give desired plasticity.

These ingredients are combined in accordance with well known ceramic methods of mixing, shapin and firing, it being noted that the low plasticity of the mixture ordinarily uires forming the superimposed layers of tl 'ie article b tamping or pressing. The in dients 0 each layer are mixed up separate y and after the first layer has been tamped in the mold, it is levelled oil? and then given a slightly rough surface to insure better uniting with the adjacent layer, the next layer placed on it and similarly treated, and so on. It is to be noted that the facing material is mixed with a. large amount of water while the backing is kept as dry as is feasible to further reduce the differential shrinkage. The article is then dried by the ordinary methods and fired at about cone 12 to vi-t-rify the bond in the facing in accordance with the usual procedure.

By carrying out the above procedure, I provide a block in which the facing is made up substantially of crystalline alumina grains bonded by vitrified clay material, the grains having been drawn together by the shrinking of the clay bond during drying and firing so that they are in substantial contact. The vitrified ceramic material, which may be modified as desired to form either a nonglassy or a vitreous bond, is present mainly in the interstices between the grains and unites integrally therewith, as is well understood in this art. The backing made by the specific formula given is similar to a fireclay brick but has a higher content of grog than ordinarily employed. The intermediate layer is made up of a mixture of the ingredients and has somewhat of the physical characteristics of each outer layer.

In an article formed of the above composition, the facing bond is in a non-glassy condition. For certain types of abrasive articles, it is desirable that the bond be of a vitreous nature. In this case, slip clay and other low melting substances may be used in the bond for the abrasive granules, the low melting ingredient serving to lower the fusion point of the mass to the firing temperature of the ceramic kiln. Owing to these ingredients being ordinarily employed in large amounts such as 20% of the mass by weight, and causing a high shrinkage of the facing, the lowshrinking material in the backing may be materially reduced in amount.

It will be obvious that changes may be made in the ingredients used and that the goportions of the different materials may varied widely within the scope of the appended claims without de rting from the spirit of this invention. %or instance, the amount of bentonite employed will depend u n the characteristics and proportions 0 the ingredients present in the other layers as well as the degree of shrinkage compensation desired. It will also be evident that I am not equalizing the shrinkage of the different portions of this brick for any temperature which may be employed, but that such equalization refers only to the temperature at which the brick is intended to be fired or used, it of course being 0bvious that it is not necessary, within the scope of this invention, that the shrinka e of the different layers be exactly alike. %f the brick is to be used for abrasive purposes or as a non-slip tile, then the temperature under consideration is that of the firing temperature, and if it is to be employed as a refractory then the shrinkage will be e ualized for a temperature of a few cones higher than that of burning. Furthermore, it is clear that the super-refractory materials covered by my claims are those which are capable of withstanding the temperature of firing the multilayer article as determined by the nature of the clay. materials present therein and of serving the purposes desired for the finished product.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent is:

1. The method of making a multilayer ceramic article having a facing of bonded granular material, comprising the steps of Incorporating with sai granular material a ceramic bond containing an ingredient capable of producing high drying shrinkage, adding water thereto to make a plastic mass, adding a backing of ceramic material, shaping the article, drying the same, and subse uently firing the mass to bond the granu es together and unite the backing therewith.

2. The method of making a multi-layer ceramic article having a super-refractory fac ing and a less refractory backin comprising the steps of superimposing a acking of plastic ceramic material and a facing of preshrunk refractory granules incorporated with a ceramic bond containin' an ingredient capable of high drying shrinitage and of equalizing the shrinkage of the two layers during the firing operation and thereafter dryin and firing the mass to bond said granu es and unite the backing therewith.

3. The method of making a multilayer article containing super-refractory grains in. one face portion only, comprising the steps of incorporating with said grains a ceramic bond containing a clay of normal shrinkage and an in redient capable of causing abnormally hig shrinkage of the bond during drying and burning, formin a moldable plastic mixture thereof, provi mg a layer of said bonded mixture with a backing of ccramic material and firing the article to bond the grains together and unite the backing integrally therewith.

4. The method of making a multilayer article, comprising the steps of incorporating with super-refractory granular material a vitrifiable ceramic bond containing an ingredient capable of swelling greatly when wctted with water, forming a plastic mixture thereof in which the grains are separated by the swollen ceramic medium, providing a ceramic backing la er therefor, drying the article, and therea er firing the article to vitrify the ceramic bond ad aCent the granuh?h and unite the backing integrally there- W1 5. The method of making an article of ceramic bonded granular material, comprisiag the defs of mixing said material with a vitrifiab e clay and bentonite, adding water thereto to form a plastic mass, shaping the article, drying the same to cause a partial shrinkage, an thereafter firing the mass to vitrify the bond and unite the granular material into an integral mass.

6. The method of manufacturing an article which has a facijn containing superrefractory grains and a acking of a difi'erent composition, comprising the ste s of incorporating with said ains a vitrifiable ceramic bond havin a igh drying shrinkage, providing a has 'ng of clay and refractory granules of low shrinkage value proportioned in amount to compensate for the igh shrinkage value of said clay and to equalize the shrinkage of the facing and backing, and firing the layers in superimposed relation to bond the super-refractory grains and unite said backing integrally therewith.

7. The method of forming a multilayer article, comprising the ste of incorporating with granular super-re ractory material a vitrifiable clay and a material capable of increasing the drying shrinkage of the mass, adding water thereto and forming a layer from the plastic mixture, mixing fire clay with a preshrunk ingredient capable of reducing shrinkage of the mixture during drying and burning, forming a backing thereof adjacent the granular facing, drying the article, and thereafter firing the article to vitrify the ceramic bond and unite the fire clay backing therewith.

8. The method of forming a multilayer article containing a preshrunk super'refractory granular material in its face portion, comprisin the steps of incorporating with said gran ar material a vitrifiable ceramic bond capable of large shrinkage during drying and burning providin a backing composition of fire c ay and regulatory granules of low shrinkage value, roportionin the amounts of the bond an and es to substantially equalize the shrinfi g ii of the two layers when fired to vitrify the bond, forming1 plastic superim d layers therefrom, rying the artic e, and thereafter firing it at a temperature to vitrify the ceramic bond and unite the backing integrallyimtherewith.

9. e method of formin a multilayer ceramic article, comprisin the steps of incorporating with super-re f raetory granular material a ceramic bond containing bentonite, providing a backing therefor of plastic ceramic material, drying the article, and firing to bond said granules and unite the backing integrally therewith.

10. The method of forming a multilayer article, comprising the steps of mixin crystalline alumina grains with a vitrifiab e clay and a materia capable of high drying shrinkage, adding water thereto and forming a plastic mixture thereof, shaping a layer therefrom, providing a ceramic backing therefor of lower refractoriness, dryin the article, and firing to vitrify the bond and unite the backing thereto.

11. The method of forming a multilayer article, comprising the steps of incorporating with su er-refractory granular material a vitrifiab e ceramic bond containing an inredient capable of high drying shrinkage, orming a plastic mixture thereof as one layer of the article, superimposing therewith a backing layer 0 fire clay and fire clay grog, and d'rymg and firing the article to vitrify the clay bond and unite the layers into an integral mass.

12. The method of forming a multilayer article, comprising the steps of harm rating with en er-refractory granular material a vitrifia le ceramic bond containing an ingredient capable of producin high drying shrinkage, forming a plastic mixture thereof as one layer of the article, superimposing thereover a layer'eontaining'a smaller amount of said super-refractory material and a larger proportion of ceramic material, forming a backing layer thereover of fire clay and fire clay grog, and drying and firing the article to vitrify the clay bond and unite the layers into an integral mass.

13. The method of forming a multilayer article, comprising the steps of mixing crystalline alumina with a vltrifiable clay and bentonite, adding water and forming a plastic laye'r thereof, superimpos' thereover a backing of vitrifiable clay an pulverized fire clay grog, drying the article, and subsequently firing at a tem rature to vitrify the ceramic bond and unite the backing integrally therewith.

14. An article of manufacture having 21. facing comprisin crystalline alumina ranules and a vitrified ceramic bond thereor containing an ingredient of high drying shrinkage, and a backing comprising granules of low refractoriness and burned fire clay integrally united with the facing.

15. An article of manufacture having a facing comprising crystalline alumina granules, a vitrified ceramic bond therefor, and a backing comprising burned fire clay and granulated fire clay 0g united with the facing by an interme iate layer of burned ceramic material.

16. An article of manufacture having a facing comprising crystalline alumina granulcs and a vitrified ceramic bond therefor, a backing comprisin burned fire clay and grog, and an interme iate layer between the facing and backing comprising burned ceramic material integrally uniting the two outer layers, said layers having had substantially the same shrinkage during drying and burning.

17. An article of manufacture having a facing comprising crystalline alumina granules, a vitrified ceramic bond therefor, a backing integrally united therewith by a burned ceramic material comprising fire clay and a preshrunk granular material of lower refractory value than that of the alumina granules, the ingredients thereof being so selected that the drying and burning shrinkage of the facing substantially equals the shrinkage of the backing.

18. An article of manufacture having a facing comprising crystalline alumina granules, a vitrified ceramic bond therefor, a backing comprising crushed mg and burned fire clay, and an interme iate layer containing fire clay, grog and alumina in lesser amounts than the outer shrinkage of adjacent layers, the layers of the article having been substantially equalized.

Signed at Worcester, assachusetts, this th day of Feb. 1921.

MACDONALD C. BOOZE.

Certificate of Correction.

It is hereby certified that in Letters Patent No. 1,459,357, granted June 19, 1923, upon the application of MacDonald C. Booze, of Worcester. Massachusetts, for an improvement in Cera'mic Articles and Methods of Making the Same, an error appears in the printed apecification requiring correction as follows: Page 5, strike out present lines 42 an 43, claim 18, and insert instead lesser amounts than the outer layers, the ahfinkage of adjacent layers of the article; and that the said Letters Patent should be read with this correetion therein that the same may conform to the record of the case in the Patent Ofiice.

Signed and sealed this 24th day of July, A. D., 1923.

m WM. A. KINNAN,

Acting flonwn'labmr of Patents. 

